### Models

Simple, equation based:
- Lotka–Volterra
- whatever Fe is the minimal of (function of protons/neutrons? discrete)
- classic predator-prey (Lotka–Volterra)
- attractors
- that vegan paper
x Uranium Critical Mass (meh, too complicated)
- urban subsidized housing (thinking in systems)
- World3 (from limits to growth report)
- Pulse Tube Cooler

Economics:
- rent control
- supply/demand curve
- World3

Harder, Time/State Based:
- Schmitt trigger (hysteresis)

Environment/Energy:
- pretty much everything from Sustainable w/o Hot Air

### Non-Model (?) Equations
- statistical distributions
- volume or surface area of platonic solids

http://equator.memeschemes.com/equation/
https://en.wikipedia.org/wiki/Category:Equations

### Constants

<copy in constants page from review of particle physics data>

https://www.wikidata.org/wiki/Q173227 (physical constant)

### Units

https://www.wikidata.org/wiki/Q15088658 (measured value)